Ruby on Rails and Docker - Why should I care?

Ruby on Rails
& Docker
Why should I care?
Adam Hodowany

About me
• Adam Hodowany
• Ruby and JavaScript developer in Monterail
• @adhodak

Docker Less
DevOps Developer story

$ bundle exec rails server -p 80
It is a joke. Please don’t do it.

http://giphy.com/gifs/ohdY5OaQmUmVW

Ruby on Rails and Docker - Why should I care?

Vagrant
• “Development environments made easy”
• Virtual Machine without overhead
• Free, local VPS for testing provisioning scripts
• Local staging

# Vagrantfile
Vagrant.configure(2) do |config|
config.vm.box = "ubuntu/trusty64"
config.vm.network "forwarded_port", guest: 80, host: 8080
config.vm.network "forwarded_port", guest: 3000, host: 3030
end
$ vagrant up
# break things
$ vagrant destroy
$ vagrant up

Ansible
• Automation tool
• Configuration using .YML files
• No client on the server

# build-server.yml
---
- hosts: all
remote_user: "{{ deploy_user }}"
roles:
### Server provisioning roles:
- { role: linux-prereqs }
- { role: postgresql }
- { role: rbenv }
- { role: ruby }
- { role: nginx }
### Site specific roles:
- { role: prepare_site }
- { role: copy-env }
- create database
- copy database.yml
- copy nginx config

Docker:
your application in a
container
Image: KMJ at the German language Wikipedia

Container
1. Application
2. All dependencies
3. Common interface
4. ???
5. PROFIT

$ bundle exec rails server
$ php artisan serve
$ python manage.py runserver
$ docker run docker-image

How is it different from VM?
Virtual Machine: Docker:
https://www.docker.com/what-docker

# Dockerfile
FROM ruby:2.2.0
RUN apt-get update -qq && apt-get install -y build-essential nodejs && gem install bundler
ENV APP_HOME /myapp
RUN mkdir $APP_HOME
WORKDIR $APP_HOME
ADD Gemfile $APP_HOME/Gemfile
ADD Gemfile.lock $APP_HOME/Gemfile.lock
RUN bundle install
ADD . $APP_HOME
CMD ["bundle", "exec", "rails", "server", "--binding", "0.0.0.0"]
- Base Image
- Copy whole application to the image
|- Default “run” command

$ docker build -t my-project .
$ docker run -p 3000:3000 my-project
host:container

Linking containers
$ docker run -d --name db postgres
$ docker run --link db:db my-project
# config/database.yml
development:
host: db
...

Volumes
$ docker run -v /home/hodak/data:/data my-project
or: shared directories
(or files)
(but most likely directories)
host:container

Docker repositories
• Docker Hub
• Official
• Free public repositories
• Alternatives exist
• Self-hosted
• Installed with… Docker
or: GitHubs for Docker images

99 official repositories including:
nginx, redis, node, postgres,
elasticsearch, wordpress,
jenkins, ruby…
Maintained by projects creators

Thousands of unofficial,
public repositories
http://gph.is/VxbrxV

Volumes are great
• My misconception: code always either in container,
or always out of it.
# Dockerfile
ADD . app_dir/
Makes sure app directory
is always in built image
Enables code reload for development
$ docker run -v $(pwd):/app_dir my-project

Docker Compose
$ docker build -t my-project .
$ docker run --link db:db -p "3000:3000" my-project

$ docker run --link db:db -p "3000:3000" --env-file .env
my-project

$ docker run --link db:db -p "3000:3000" --env-file .env -
v /home/hodak/code/my-project:/my-project my-project

$ docker run -d --name redis redis
$ docker run -d --name sidekiq --link redis:redis --link db:db --env-file
.env my-project bundle exec sidekiq
$ docker run --link db:db --link redis:redis -p "3000:3000" --env-file .env
-v /home/hodak/code/my-project:/my-project my-project

# docker-compose.yml
db:
image: postgres
web:
build: .
command: bundle exec rails server --binding 0.0.0.0
ports:
- "3000:3000"
links:
- db
volumes:
- .:/myapp
env_file: .env
$ docker-compose build
$ docker-compose up

# docker-compose.yml
db:
image: postgres
redis:
image: redis
sidekiq:
build: .
command: bundle exec sidekiq
volumes:
- .:/myapp
links:
- db
- redis
env_file: .env
web:
build: .
command: bundle exec rails server --binding 0.0.0.0
ports:
- "3000:3000"
links:
- db
- redis
volumes:
- .:/myapp
env_file: .env

Use Cases
• Ruby on Rails agency - meh?
• Microservices
• Especially in different technologies
• Working with Freelancers

Admesh
github.com/admesh/admesh

$ ./configure
$ make
$ make install

# Dockerfile
COPY ./lib/admesh-0.98.2.tar.gz $APP_HOME/admesh.tar.gz
RUN tar -zxvf admesh.tar.gz &&
cd $APP_HOME/admesh-0.98.2 &&
./configure &&
make &&
make install

Continuous Integration
with Docker

Typical Rails-CI setup
$ cp config/codeship.database.yml config/database.yml
$ rvm use 2.1.1
$ bundle install
$ export RAILS_ENV=test
$ bundle exec rake db:drop db:create db:structure:load
$ bundle exec rspec

Development CI
Ruby version
Bundler version
Ruby version
Bundler version

Development CI
Ruby version
Bundler version
Ruby version
Bundler version
Staging Production
Ruby version
Bundler version
Ruby version
Bundler version

• More tricky dependencies
• ImageMagick
• ADMesh
• …

Development CI Docker Repository
Dev
Build
Productio
n
Build
Staging Production

• Image that has proven itself
• No errors
• Specs passed

$ cp config/codeship.database.yml config/database.yml
$ rvm use 2.1.1
$ bundle install
$ export RAILS_ENV=test
$ bundle exec rake db:drop db:create db:structure:load
$ bundle exec rspec

- Start Postgres
|- Build production image
- Set up database
- Run specs
After specs pass:
Send image
to Docker Hub
# origin/master -> master
$ BRANCH_NAME=`echo $GIT_BRANCH | cut -d '/' -f 2-`
$ docker rm --force $(docker ps -aq) || echo "ok"
$ docker build -t my-project -f Dockerfile.prod .
$ docker run --link db:db -e RAILS_ENV=test my-project bundle exec rake db:create d
$ docker run --link db:db -e RAILS_ENV=test my-project bundle exec rspec
$ docker tag my-project hodak/my-project:$BRANCH_NAME
$ docker push hodak/my-project:$BRANCH_NAME

# build-server.yml
---
- hosts: all
roles:
- { role: postgresql }
- { role: rbenv }
- { role: ruby }
- { role: nginx }

# build-server.yml
---
- hosts: all
roles:
- { role: nginx }
- { role: docker }
- create database
- copy database.yml
- copy nginx config

• Still must configure nginx
• Pull image from Docker repository
• Not touching GitHub at all
• Synchronise starting containers
• Monitoring

Data-only container pattern
$ docker run --name dbdata postgres echo "Data-only container for
postgres"
$ docker run -d --volumes-from dbdata --name db postgres

#!/bin/bash
docker run --name dbdata postgres echo "Data-only container for
postgres" || echo "already started"
docker run -d --volumes-from dbdata --name db --restart=always
postgres || docker start db
docker pull hodak/my-project:master
docker tag hodak/my-project:master my-project
docker run --link db:db my-project bundle exec rake db:create
db:migrate
docker rm --force my-project || echo "not yet created"
docker run -d --link db:db --name my-project --restart=always --env-file
.env -p "8080:8080" my-project

tasks:
- name: application container
docker:
name: my-project
image: hodak/my-project:master
state: reloaded
pull: always
links:
- "db:db"
ports:
- "8080:8080"
restart_policy: always

Custom deploy script
for Capistrano

upstart / systemd /
supervisor / monit

Thank you!
Questions?
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Ruby on Rails and Docker - Why should I care?

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